United States Patent Applications 2002/0001684 (Jan. 3, 2002), 20030134966 (Jul. 13, 2003) and 20050106343 (May 19, 2005), all of which have a common inventor Kim, teach a composition of PET (A), a polyamide, MXD6 nylon (B), with cobalt octoate. The Kim series of applications teach that when the PET/MXD6/Cobalt octoate composition is injected molded into a preform (parison) and then oriented (stretched) into a blown bottle, the resultant bottle is hazy. The Kim applications also identify the cause of the haze. According to Kim, the haze is caused by the MXD6 domains dispersed into the PET which upon orientation have been stretched to the point where the size of the domains are greater than the wavelength of light.
Kim et al teaches that smaller domains reduce the haze caused by the previously large domains. One of ordinary skill knows there are two ways to have smaller domains in the stretched bottle. One is to reduce the size of the starting domains in the preform or parison, the other is to not orient or stretch the bottle as much. The solution selected in the Kim series of applications to replace the injection blow process of making the preform/parison and subsequently orienting(stretching) the preform into a blown bottle with a much lower stretch process called extrusion blow.
The Kim applications also teach that a container made with PET/MXD6/Cobalt octoate exhibits higher oxygen barrier (lower permeation rate) presumably due to the well known ability of the cobalt octoate to catalyze the reaction of MXD6 nylon with oxygen. While Kim et al, therefore teaches that reducing the size of the MXD6 domains as a way to reduce the haze in stretched containers, it does not teach how to solve the haze in an injection blown container or how to reduce the size of the domains in an injection blown container, presumably because this was already known in the art prior to the invention of Kim.
JP-2663578-B2 (Oct. 15, 1997) to Yamamoto et al identifies the same problem as the Kim applications with the same composition. Yamamoto et al discloses that a hazy stretch blown bottle is created when a composition of polyester (A) and MXD6 nylon (B) is injection molded into a parison (preform) and oriented (stretched) into a bottle. Recall that Kim et al teach that this haze is cause by large domains and the only difference being that the bottle of Kim et al contains cobalt octoate.
Yamamoto et al, then teaches that the haze in the PET/MXD6 injection blown bottle may be eliminated by incorporating a third polyester component (C) wherein the third polyester component has 5-sodium sulfoisophthalate derived from 5-sodium sulfoisophthalic acid in its polymer chain. The copolymerization of the 5-sodium sulfoisophthalic acid is taught in Table 3 of Yamamoto with the conclusion being: when polyester copolymerized with 5-sodium sulfoisophthalate is used as the component (C), the transparency is improved and the haze is notably reduced. One of ordinary skill would therefore solve the haze of Kim's injection molded/stretch blown bottle containing PET/MXD6/cobalt octoate by adding the polyester (C) copolymerized with 5-sodium sulfoisophthalate taught by Yamamoto et al. One would not eliminate the cobalt octoate found in the Kim applications because that would reduce the oxygen barrier of the container.
U.S. Pat. No. 5,300,572 (Apr. 5, 1994) to Tajima et al teaches how to reduce the domain size of a polyamide dispersed into a polyester. Tajima et al reduces the domain size of the polyamide by adding sodium sulfoisophthalic acid, either copolymerized into the backbone of polyester (A) or as a third component (C) which is a polyester copolymerized with the sodium sulfoisophthalic acid. Since the Kim applications teaches that reducing the size of the polyamide domains solves the haze one of ordinary skill wishing to make an injection molded/stretch blown bottle containing PET/MXD6/Cobalt octoate would either use a PET copolymerized with sodium sulfoisophthalate derived from sodium sulfoisophthalic acid for the A component as taught by Tajima et al or add a polyester (C) copolymerized with sodium isophthalate as taught by Yamamoto et al. Again, one would not eliminate the cobalt octoate of Kim et al because that would reduce the increased oxygen barrier of Kim et al.
WO 2005/023530 (Mar. 17, 2005) to Mehta et al teaches that a cobalt salt is essential when injection molding a preform (parison) comprising the composition of Kim et al [a polyester (A), a polyamide such as MXD6 (B)], and in the presence of an ionic compatibilizer such as 5-sodium sulfoisophthalic acid or 5-sodium sulfoisophthalate. Mehta et al and Kim et al even use the same cobalt salt—cobalt octoate. According to Mehta et al, a large amount of yellow colour is created when combining the polyester (A), with polyamide (B) in the presence of an ionic compatibilizer (C) and the use of the cobalt octoate also taught in the Kim applications prevents that colour formation.
While the use of cobalt may alleviate colour, it inherently creates an active barrier package. There are other active barrier mechanisms, such as oxidizing an elemental metal in the wall of the container. Since there are packaging applications which do not benefit and are in fact harmed by an organic scavenger or need a less powerful active package; there exists, therefore, the need for an MXD6/polyester ionic compatibilizer where cobalt is not necessary to prevent the detrimental colour formation noted in Mehta et al.